Dosimetric comparison between intensity modulated radiation therapy and three-dimensional conforreal radiotherapy in non-small cell lung cancer

Abstract

Objective To investigate whether intensity modulated radiation therapy (IMRT) is su-perior to three-dimensional conformal radiotherapy (3DCRT) in dosimetry for non-small cell lung cancer (NSCLC). Methods Twenty-one stage Ⅰ-Ⅲ NSCLC patients were enrolled in this study. The prescrip-tion dose of 3DCRT was 65 Gy and the dosimetric demands for targets and normal organs were satisfied. Step and shoot technique was used and seven equal-spaced coplanar beams were chosen for IMRT planning. The dose constraints of the normal lungs for IMRT were set according to V 5 -V 60 of the normal lungs obtaining from the same patient's 3DCRT dose volume histogram. The prescription dose for IMRT was started from 65 Gy, and then escalated or decreased step by step by 2 Gy once a time until the best plan was obtained. Re-suits Compared to 3DCRT, IMRT had lower V 5 -V 60 , mean dose, normal tissue complication probability of the normal lungs and lower V 55 , mean dose of the esophagus. The two plans had comparable heart V 40 and maximum dose to the spinal cord. Both conformity index and heterogeneity index of the targets were increased by IMRT. IMRT had higher total monitor units than 3DCRT. IMRT could escalate prescription dose by (5.1 ±4.6) Coy. Conclusions The use of IMRT in NSCLC can spare more volume of the normal lungs and e-sophagus, and has the ability of dose escalation. Key words: Lung neoplasms/radlotherapy; Radiotherapy; three-dimensional conformal ; Radiotherapy; intensity modulated; Dosimetry